Sciarid fly larvae in growing media - biology, occurrence, substrate and environmental effects and biological control measures

Transcription

1 Sciarid fly larvae in growing media - biology, occurrence, substrate and environmental effects and biological control measures The black fungus gnat Bradysia difformis (Frey, 1948) (= B. paupera) is one of the most common types of fungus gnats occurring in protected cultivation of ornamental plants, potted herbs and other greenhouse plants. Although the species is primarily mycophagous, root feeding by the larvae can result in considerable yield losses. Adult black fungus gnats often pose a hygiene problem in greenhouses and occur as pests in commercial and residential buildings. The massive and thus injurious occurrence of this species in greenhouses is always associated with the previous incidence of severe fungal mycelia growth in the substrate or roots of the plants. Adult black fungus gnats selectively deposit their eggs on the fungal mycelium and actively contribute to its proliferation by spreading the spores adhering to their bodies around the greenhouse. Phytopathogenic fungi such as Botrytis cinerea, Fusarium species and Phoma betae are preferably used for oviposition. Inversely, fungi such as Sclerotinia sclerotiorum, Chaetomium olivaceum and Trichoderma viride are non-preferred nutrient sources for these fungus gnats. Typical compost fungi such as Alternaria alternata und Fusarium filiferum are also an ideal source of larval nutrition, whereas Aspergillus sp., Mucor sp. Penicillilium crustosum and Ulocladium consortiale are unsuitable sources. A simple mass rearing method is to use coconut fiber or wood fiber as the substrate and add only natural oat flakes. The mycelium subsequently growing on the oat flakes in the moist substrate provides an ideal food source for fungus gnats. In practice, black fungus gnats are controlled using nematodes (Steinernema feltiae), predatory mites (Hypoaspis miles or H. acaulifer) or bacteria (Bacillus thuringiensis var. israelensis). But also predatory flies of the genus Coenosia (Diptera: Muscidae) often natural occurring in greenhouses can control Sciarid fly larvae very effective. Among the biological pesticides, Neem extracts (Azadirachta indica) have achieved very good control results in contrast to Quassia extracts (Quassia amara).

2 Titel zweizeilig eingeben (Schriftgröße, Arial fett, mindestens 18pt) Hier Text eingeben Schriftgröße Arial, mindestens 14pt, möglichst 16 pt oder mehr, Zeilenabstand: mindestens 1,1 Zeilen SCIARID FLY LARVAE IN GROWING MEDIA - BIOLOGY, OCCURRENCE, SUBSTRATE AND ENVIRONMENTAL EFFECTS AND BIOLOGICAL CONTROL MEASURES Stefan Kühne & Kai Heller stefan.kuehne@jki.bund.de kaiheller@gmx.de Institute for Strategies and Technology Assessment in Plant Protection Stahnsdorfer Damm 81, Kleinmachnow

3 Federal Research Centre for Cultivated Plants Julius Kuehn-Institute (JKI) Institutes: 15 specialized institutes Budget (1st Jan 2009): Federal budget 62 Mio, third-party funds 5 Mio, total 67 Mio Staff (1st Jan 2009): Permanent posts 831, total staff 1.150, scientists about 250

4 Black fungus gnat Bradysia difformis (Frey, 1948) (= B. paupera) 1996 Bradysia difformis (Frey, 1948) (= B. paupera), female Ventral hypopygium of male Bradysia difformis (Frey, 1948) (= B. paupera): Illustration by Menzel in: Kühne et al. (1994) B. difformis is the most common species of black fungus gnats in green houses

5 Development cycle of Bradysia difformis 5 6 days pupa about 100 eggs imago 3 7 days days 5 7 days larvae development cycle is completed in days generation / year in green houses

6 Oviposition of Bradysia difformis for egg deposition mycelium of suitable fungi are preferred

7 Egg-laying and larval feeding activity in the microorganisms cultivated on petri dishes Test-Organism Egg-laying Feeding activity Phytopathogenic fungi: Botrytis cinerea Pers Fusarium culmorum (W.G.Sm.) Sacc Fusarium cerealis (Cooke) Sacc Fusarium avenaceum (FR.) Sacc Phoma betae (Oud.) Frank Rhizoctonia solani Kühn Sclerotinia sclerotiorum (Lib) de By. + + Other microbial fungi: Chaetomium olivaceum Cooke et Ellis + + Trichoderma viride Pers. ex Fr. (+) + Soil bacteria: Bacillus pumilis Gottheil (+) - Pseudomonas fluorescens Migula (+) - Control (no test organisms) > 300 eggs/dish; complete consumption to 300 eggs/dish and extensive mycelial damage eggs/dish and visible mycelial damage (+) Few eggs/dish and insignificant feeding activity - No egg-laying and no feeding activity fungi with high mycelium growing are a good food source for fungus gnats

8 Larval feeding activity of B. difformis on the fungus Fusarium aveneceum control larvae Larval feeding activity of B. difformis on the fungus Fusarium aveneceum (A) 2 days and (B) 6 days after feeding of fungus gnats larvae

9 Survival rate of microorganisms following larval feeding by fungus gnats Test organism Phytopathogenic fungi: Survival rate*) Botrytis cinerea Pers. 7 % Fusarium culmorum (W.G.Sm.) Sacc. 10 % Phoma betae (Oud.) Frank 3 % Rhizoctonia solani Kühn. 0 % Sclerotinia sclerotiorum (Lib) de By. 13 % Other microbial fungi: Chaetomium olivaceum Cooke et Ellis 63 % Trichoderma viride Pers. ex Fr. 91 % Soil bacteria: Bacillus pumilis Gottheil 100 % Pseudomonas fluorescens Migula 100 % *) 20 samples per petri dish (in triplicate). Fungi were transferred to SNA medium and bacteria to King's B medium. Fungi growing is negativ influenced by fungus gnat feeding

10 Egg-laying and larval feeding activity and development of fungus gnats on compost fungi Test organism Egg-laying Feeding activity Imago/ petri dish*) Alternaria alternata (Fr.) Kreissler Aspergillus sp. (+) (+) 3 Cladosporium herbarium (Pers.) Link ex S.F. Gray Fusarium filiferum (Pr.) Wollenw Mucor sp Penicillium crustosum Thom (+) (+) 13 Rhizopus stolonifer (Ehrh. ex Fr.) Lind Ulocladium consortiale (Thüm.) Simmons Control (no test organisms) Legend: +++ > 300 eggs/dish; complete consumption to 300 eggs/dish and extensive mycelial damage eggs/dish and visible mycelial damage (+) Few eggs/dish and insignificant feeding activity - No egg-laying and no feeding activity *) development time of B. difformis from egg to imago 18 days also compost fungi with high mycelium growing are a good food source for fungus gnats

11 Mass rearing method for fungus gnats + 8 l of water + coconut coir = oat flakes oat flakes Black fungus gnat

12 Biological control of black fungus gnats by beneficial arthropods and bacteria Important black fungus gnats Natural species enemies Bradysia difformis (= B. paupera) Nematodes Lycoriella ingenua (= Ly. solani) Predatory soil mites Bacteria Steinernema feltiae Hypoaspis miles oder H. acaulifer (B.t.i.) 0,25 0,5 Mill Nematodes / m nematodes / l container substrate Hypoaspis / m ml Neudomück / 100 m 2

13 Biological control of black fungus gnats by botanical insecticides Neem tree - Azadirachta indica NeemAzal -U 0.3% (2 x week for 5 weeks) have been successfully tested to control fungus gnats Bitterwood - Quassia amara 8% Quassia no effect

14 Predatory flies natural occurring in green houses and feeding on black fungus gnats Stilpon nubila Platypalpus pallidicornis Platypalpus annulatus Platypalpus pallidiventris

15 Coenosia attenuata Stein

16 Mouth disc of Coenosia dagger like tooth rasp tongue lateral praestomal teeth dagger like tooth dorsal rasp tongue praestomal teeth

17 Notices about global occurrence of Coenosia Canada, USA, Peru ornamental plants Germany ornamental plants, vegetable crops Portugal vegetable crops Spain vegetable crops Italy ornamental plants Turkey cotton fields, pot herbs Thailand ornamental plants

18 open rearing Thailand

19 the garden of Europe Almeria, Spain

20 2008 Orchids Antura in Germany

21 2008 Orchids Antura in Germany

22 2009 potherbs, Antalya, Turkey

23 2009 potherbs, Antalya, Turkey

24 Development cycle of C. attenuata 10 d 25 C Pupa 10 d 6 d Egg Larva

25 Larvae of Coenosia also predatory! hatching larva Coenosia-larva feed on fungus gnat (Bradysia)

26 Average predatory consumption rate of adult Coenosia 8 Average of 22 days α = 0,95 6 7,7 prey / day ,2 1,5 1,8 C. atra C. attenuata C. strigipes Bradysia Drosophila

27 Summary I Bradysia difformis (Frey, 1948) (= B. paupera) is one of the most common types of fungus gnats occurring in protected cultivation of ornamental plants, potted herbs and other greenhouse plants Fungus gnats primarily mycophagous, root feeding by the larvae can result in considerable yield losses Massive occurrence of fungus gnats in greenhouses is always associated with the previous incidence of fungal mycelia growth in the substrate or on roots of the plants Fungus gnats are boosted by additives of manure promote fungal mycelia growth in the substrate

28 Summary II Fungus gnats are controlled by using nematodes (Steinernema feltiae), predatory mites (Hypoaspis miles or H. acaulifer), bacteria (Bacillus thuringiensis var. israelensis) Neem extracts (Azadirachtin) have achieved very good control results of fungus gnats in contrast to Quassia extracts (Quassia amara) Predatory flies of the genus Coenosia (Diptera: Muscidae) often naturally occurring in greenhouses can control fungus gnats very effective